A drilling auxiliary system

ABSTRACT

The present invention provides a drilling auxiliary system, which is used for down hole EM data transmission and/or casing detection, wherein said drilling auxiliary system comprises an insulating device which is mounted on the drill pipe of a well and used for preventing entire electric current loss or suppressing partial electric current loss. When used for EM data transmission, the present invention can greatly reduce the unnecessary power consumption, thereby improving the efficiency of EM data transmission. When used for casing detection, the present invention can effectively increase the casing detection range.

FIELD OF THE INVENTION

The invention relates to the technical field of petroleum drilling, and particularly, to a drilling auxiliary system for down hole electromagnetic (EM) data transmission and casing detection.

BACKGROUND OF THE INVENTION

Logging While Drilling(LWD) in petroleum industry generally refers to the technique to measure the formation geophysical parameters in the process of drilling, and to transmit the real-time measure results back to the surface by a data telemetry system.

One of the key techniques of LWD is signal transmission. currently, Mud-pulse telemetry is widely applied in the industry, which converts the data measured by LWD instruments into the mud pressure pulses and then transmits them back to the surface through the mud circulation system. Mud-pulse telemetry is economical and convenient, but its data transmission rate (the number of bits transmitted per second) is very low.

To improve the transmission rate, a new data transmission method, EM telemetry, is developed, which uses EM waves to transmit data between down hole and earth surface. FIG. 1 shows a typical EM telemetry system in the prior art, in which an insulation ring 2 is arranged on the drill pipe 5 above the drill bit 4, which divide the drill pipe into two mutually insulated segments. A low-frequency power supply 3 is loaded between both ends of the insulation ring. As the arrows in the figure indicate the formation (refers to the formation from the vicinity of both ends of the insulating ring 2 to the infinitude of the ground), pipe, and the power supply form a loop. The arrowed lines show the current distribution in the formation, wherein, the bold arrows indicate higher current intensity, the thin arrows indicate low current intensity, and the current intensity indicated by the dotted arrows is weaker than that indicated by the solid arrows. Due to the current being symmetrically distributed on both sides of the drill pipe and the casings(for non-symmetrical formations, such as large angle drilling, the distribution will vary, but it will not affect the conclusion, so it is not discussed here), for simplicity, FIG. 1 only shows the current distribution on the left side of the drill pipe. As shown in FIG. 1, the current intensity in the sub-loop near the insulating ring 2 is higher, and the current intensity in the sub-loop far away from the insulating ring 2 is lower. When the well being drilled is relatively deep(such as more than 2000 meters), the current in the sub-loop through the vicinity of the ground surface will be very weak. The down hole data is loaded on the power supply, and then is transmitted to the ground surface through the electromagnetic field generated by the current. The surface terminal A of casing 1 of the well being drilled is connected to one terminal of the signal receiver 10, and the other terminal of the signal receiver 10 is connected to an infinitely far ground terminal B. In this way, the down hole data can be obtained by measuring the changes of the voltage between terminal A and B. However, because the current density of the sub-loop through the vicinity of the ground surface is very small, the signal receiver 10 is required to be extremely sensitive, and the data transmission rate is very limited.

The down hole casings of nearby existing wells is often required to be located in the drilling process. There are two relatively matured techniques for down hole casing ranging. One is to put a transmitting device into the existing wells, which generates an electromagnetic field in the formation. Meanwhile, a receiving device is placed on the pipe of the drilling well, which can detect the electromagnetic field and thus determine the location of the already existing wells. This method has a large detection range, but the operation is complicate with high cost. The other technique is to place both the transmitting device and the receiving device on the pipe of the drilling well. The transmitting device generates an EM field in the formation, the EM field generates an induced current in the casing of the existing well, and then the induced current will produce a secondary EM field in the formation. The secondary EM field captured by the receiving device can be used to locate the casing of the existing well. This method is relatively simple, but the detection range is greatly reduced.

SUMMARY OF THE INVENTION

An object of the invention is to overcome the shortcomings of the prior art and provide a solution for efficient down hole EM data transmission and/or casing detection.

In order to achieve the above object, the present invention provides a drilling auxiliary system, which is used for down hole EM data transmission and/or casing detection, wherein said drilling auxiliary system comprises an insulating device, which is mounted on the drill pipe of a well and used for preventing entire current loss or suppressing partial current.

Wherein said insulating device blocks or suppresses current flowing between the drill pipe and the medium surrounding the drill pipe, or blocks/suppresses current flowing between the drill pipe and the medium inside the drill pipe.

Wherein said medium surrounding the drill pipe comprises formation around the drill pipe, said medium inside the drill pipe comprises mud inside the drill pipe.

Wherein said insulating device surrounds said drill pipe, being embedded into the wall of the drill pipe, or mounted on a position clinging to the drill pipe, or mounted on a position separated from the drill pipe.

Wherein said the drill pipe is tubular, and said insulating device comprises an outer insulating device and an inner insulating device, wherein said inner insulating device surrounds the inner wall of said the drill pipe, wherein said inner insulating device is embedded into the inner wall of said drill pipe, or mounted on a position clinging to or separated from the inner wall of said drill pipe; and wherein said outer insulating device surrounds the outer wall of said drill pipe, wherein said outer insulating device is embedded into the outer wall of said drill pipe, or mounted on a position clinging to or separated from the outer wall of said drill pipe.

Wherein said insulating device partially or completely covers the transmitting and receiving instruments mounted on the drill pipe.

Wherein said insulating device surrounds the enwrapped drill pipe segment with completely 360 degrees, or partially surround the enwrapped drill pipe segment with less than 360 degrees.

Wherein said insulating device is an insulating sheet with particular shape, for blocking the current in a particular azimuth.

Wherein the shape of said insulating sheet is square or ellipse, or any other shape.

Wherein there are one or more gaps on said insulating device, and said one or more gaps allow the current to pass.

Wherein said gaps on said insulating device may be any shape.

Wherein said gaps on said insulating device may locate at any positions on said insulating device.

Wherein said gaps on said insulating device are used for controlling the direction and/or the position of current flowing in or out.

Wherein said insulating device enwraps or partially enwraps the insulating ring on the drill pipe and partial or whole drill pipe segments, which extend from the insulating ring in both directions.

Wherein said insulating device enwraps or partially enwraps the insulating ring and partial or whole drill pipe segment, which extends from the insulating ring in one direction.

Wherein said insulating device enwraps partial or whole drill pipe segment which extends from the insulating ring in one direction.

Compared with the prior art, the invention has the following technical effects:

1. When used for EM data transmission, the present invention can greatly reduce the unnecessary consumption of electrical energy; thereby improve the efficiency of electromagnetic data transmission.

2. When used for casing detection, the present invention can effectively increase the casing detection range.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a typical down hole EM telemetry system in the prior art.

FIG. 2 shows a schematic diagram of the current distribution of a drilling auxiliary system which connects the drilling well with a exist well.

FIG. 3 shows a schematic diagram of an EM telemetry system in an embodiment of the present invention.

FIG. 4 shows a schematic diagram of an improved drilling auxiliary system in an embodiment of the present invention.

FIG. 5 shows a schematic diagram of a drilling auxiliary system in another embodiment of the present invention, which implements efficient data transmission.

FIG. 6 shows a schematic diagram of a drilling auxiliary system in still another embodiment of the present invention, which implements efficient casing detection.

FIG. 7 shows a schematic diagram of a drilling auxiliary system in yet another embodiment of the present invention, which implements efficient casing detection.

FIG. 8 shows a schematic diagram of a drilling auxiliary system in yet another embodiment of the present invention, which implements efficient casing detection.

FIG. 9 shows a schematic diagram of a drilling auxiliary system in yet another embodiment of the present invention, which implements both efficient data transmission and casing detection.

FIG. 10 shows a schematic diagram of a drilling auxiliary system in yet another embodiment of the present invention, which implements both efficient data transmission and casing detection.

FIG. 11 shows a schematic diagram of a drilling auxiliary system adapted to connect different branches of the same well, in yet another embodiment of the present invention, which can implement efficient data transmission.

FIG. 12 shows a schematic diagram of a drilling auxiliary system adapted to connect different branches of the same well, in yet another embodiment of the present invention, which implements casing detection of the existing branch.

FIG. 13 shows a schematic diagram of a drilling auxiliary system adapted to connect different branches of the same well, in yet another embodiment of the present invention, which implements both data transmission and casing detection.

FIG. 14 a˜f show schematic views of insulating device mounted on the drill pipe in a preferred embodiment of the present invention. Wherein FIG. 14a shows a longitudinal sectional view of drill pipe on which a surrounding insulating device is mounted, and the FIG. 14 b˜f shows transverse sectional views with respect to the A-A′ section in FIG. 14a of drill pipe on which a surrounding insulating device is mounted.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention will be further described in conjunction with embodiments with reference to accompanying drawings.

FIG. 3 shows a schematic diagram of a down hole EM data transmission system in an embodiment of the present invention. Like FIG. 1, FIG. 3 only shows the current distribution on one side of the drill pipe. According to FIG. 3, the down hole EM telemetry system of the present embodiment comprises an insulating device 17, which surrounds drill pipe 5 with 360 degrees. The insulating device 17 clings to the drill pipe 5, or maintains a certain distance from the drill pipe 5, or is built into the drill pipe 5 as a part of it. In this embodiment, insulating ring 2 and the drill pipes connected to the insulating ring 2 on both sides are enwrapped by insulating device 17. Because the insulating device 17 suppresses the electric current flowing between the drill pipe and the formation nearby, the formation nearby the power source cannot form a loop like FIG. 1. Therefore, more current is forced to flow along the drill pipe in the directions away from the both ends of the power source, and thereby the current intensity of other regions is increased. Since the power loss rate in the formation nearby the power source is biggest, suppressing this part unnecessary loss can greatly enhance the desired current intensity near the ground surface, further effectively increases the efficiency of down hole data transmission.

According to another embodiment of the present invention, a drilling auxiliary system is provided, which is an improvement of a drilling auxiliary system involved in another patent application of the present inventor. For ease of understanding, the drilling auxiliary system involved in said another patent application hereby is briefly introduced. FIG. 2 shows the schematic diagram of the electric current distribution of the drilling auxiliary system involved in said another patent application, in which, in currently drilling well 1, an insulating ring 2 is set on the drill pipe 5 so as to divide the drill pipe 5 into two mutually insulated segments(upper segment and lower segment), and a power source 3 connects the upper segment and the lower segment of the drill pipe (the two junction points between power source 3 and the drill pipe segments locate at the positions close to the both ends of the insulating ring 2,as shown in FIG. 2). The well head terminal A of the casing 7 of currently drilling well 1 is connected with the well head terminal B on the casing 8 of an existing well 6 by a wire, and a signal receiver 10 is serially connected between terminal A and B. Thus power source 3, the pipe 5 of currently drilling well 1, the casing 7 (usually a conductor) of currently drilled well 1, the wire between the two wells, the casing 8 of already existing well 6 and the formation between the two wells form a large loop, in which the energy dissipation in the formation is much smaller than that of the traditional EM telemetry system. Therefore, the drilling auxiliary system can transmit data efficiently. In particular, with reference to FIG. 2, there includes two current sub loops. The first loop is that: the current outflows out from the upper terminal of the power source, passes through the upper drilling pipe 5, wires on the ground surface, the casing of the existing wells, the formation and the lower drill pipe, and finally returns to the power source, thereby forming a loop; the second loop is that: the electric current outflows out from the upper terminal of the power source, then passes through the upper drilling pipe, the formation and the lower drill pipe, and finally returns to the power source, thereby forming a loop. Since the power in the first loop is mainly consumed in the formation between the down hole casing of the existing well and the lower drilling pipe. When the distance is not far between the existing well and the drilling well, the current in this loop is large enough to be detected. Most of this current flows through the connection wire between the currently drilled well and the existing well, so down hole MWD (measurement while drilling) information loaded on power source is easily received by the ground surface receivers, so as to achieve signal transmission effect. Since the current in the first loop is relatively strong, it is possible to load a relatively high frequency signal, which increase the transmission efficiency. In FIG. 2, the current in the vicinity of the ground surface, which flows from currently drilling well through formation to already existing well, is very small, so it is represented by lighter arrows.

FIG. 4 shows a schematic diagram of an improved drilling auxiliary system in an embodiment of the present invention. Compared with the example of FIG. 2, an insulating device 17 is added in the present embodiment. Similar to the embodiment of FIG. 3, the insulating device 17 in present embodiment also surrounds drill pipe 5 with 360 degrees, which enwraps the insulating ring 2 and both upper and lower segments of the drill pipe 5 close to the insulating ring 2. The insulating device 17 suppresses the current flow between the drill pipe and the formation near the source, so no loop can be formed nearby the source as FIG. 2. Therefore, more current is forced to flow along the drill pipe in the directions away from both ends of the power source, and thereby the current intensity in other regions increase. Since the current on connection wire AB between wells is increases, and this part of current can transmit data, the efficiency of data transmission can be effectively enhanced when the drilling auxiliary system of the present embodiment is used for transmitting data.

FIG. 5 shows a schematic diagram of a drilling auxiliary system in another embodiment of the present invention, which can implement effective data transmission. The difference between the present embodiment and the embodiment of FIG. 4 is that: in the present embodiment, a signal receiving device 10 is serially connected to the wire between the wells, thus the down hole data loaded on low-frequency power source 3 can be received on the ground. Other structures and the current distribution of the present embodiment are the same with those of the embodiment of FIG. 4, and will not be described repeatedly herein.

FIG. 6 shows a schematic diagram of a drilling auxiliary system in yet another embodiment of the present invention, which implements efficient casing detection. The difference between the present embodiment and the embodiment of FIG. 5 is that: no signal receiving device 10 is placed on the connecting wire between the wells, and a casing detection receiver 11 is mounted on the drill pipe segment which is above, and not enwrapped by insulating device 17. Other structures and the current distribution of the present embodiment are the same with those of the embodiment of FIG. 5. When current flows to an existing well, it will flow down along the casing of the already existing well, and pass through the formation to the drill pipe below the power source of the drilling well, then flow back to the power source. Quite a part of current flows through the casing of existing well, which generates an EM filed. Casing detection receiver 11 on the drilling well can detect that EM field, and further determine the distance and azimuth of the already existing well. In the present embodiment, by adding the insulating device 17, the current in the casing 8 of the existing well 6 will be enhanced. Thus, when the drilling auxiliary system of the present embodiment is used for casing detection, the detection range can be effectively extended. Moreover, the present embodiment can ensure a certain effective detection range without additional sophisticated instruments, and doesn't need to stop the operations of the existing well, therefore the detection cost will be greatly reduced.

FIG. 7 shows a schematic diagram of a drilling auxiliary system in yet another embodiment of the present invention, which can implement effective casing detection. The difference between the present embodiment and the embodiment of FIG. 5 is that: a casing detection receiver 11 is added to the drill pipe segment which is beneath and not enwrapped by insulating device 17. Other structures and the electric current distribution of the present embodiment are the same with those of the embodiment of FIG. 5, and will not be described repeatedly herein.

FIG. 8 shows a schematic diagram of a drilling auxiliary system in yet another embodiment of the present invention, which can implement effective casing detection. The difference between the present embodiment and the embodiment of FIG. 6 is the different mounting position of the casing detection receiver 11 in the present embodiment, where the casing detection receiver 11 is loaded to the drill pipe segment enwrapped by insulating device 17. Other structures and the electrical current distribution of the present embodiment are the same with those of the embodiment of FIG. 6, and will not be described repeatedly herein.

FIG. 9 shows a schematic diagram of a drilling auxiliary system in yet another embodiment of the present invention, which can implement both effective down hole data transmission and effective casing detection. The difference between the present embodiment and the embodiment of FIG. 6 is that: a signal receiving device 10 is added to (or to the vicinity of) the connecting wire between wells. In addition, in the system of the embodiment, an auxiliary power source 12 is provided on the ground surface. The auxiliary power source may increase the strength of the useful signal, and as well as the current intensity on the casing of already existing well. Thus it may increase the data transmission rate and extend the effective casing detection range. Other structures and the current distribution of the present embodiment are the same with those of the embodiment of FIG. 6, and will not be described repeatedly herein.

FIG. 10 shows a schematic diagram of a drilling auxiliary system in yet another embodiment of the present invention, which can implement both effective down hole data transmission and effective casing detection. The difference between the present embodiment and the embodiment of FIG. 9 is that: insulating device 17 surrounds a partial drill pipe segment till one end of insulating ring 2. Other structures of the present embodiment are the same with those of the embodiment of FIG. 9, and will not be described repeatedly herein.

FIG. 11 shows a schematic diagram of a drilling auxiliary system adapted to connecting different branches of one well in yet another embodiment of the present invention, which implements effective data transmission. The principle of the system is the same with the principle of different wells being connected mutually by wires. Signal receiving device 10 of the system may be placed on the connection wire between two branches, or may be placed on the ground surface and is connected by a cable to the connection wire between two branches, as shown in FIG. 11. In the present embodiment, data transmission is implemented by measuring the voltage change between the infinity 9 and the connection wire between two branches. Numeral 15 represents a branch of an already existing well, numeral 16 represents a casing of an existing branch, numeral 13 represents a currently drilling branch, and numeral 14 represents the casing of a currently drilling branch.

FIG. 12 shows a schematic diagram of a drilling auxiliary system adapted to connecting different branches of one well in yet another embodiment of the present invention, which implements casing detection of existing. The system is similar to that shown in FIG. 11, and the difference is that: in FIG. 12, a casing detection receiver 11 is mounted on the drill pipe segment above the insulating device of the currently drilling branch and the signal receiving device 10 is removed. Other structures of the present embodiment are the same with those of the embodiment of FIG. 11, and will not be described repeatedly herein.

FIG. 13 shows a schematic diagram of a drilling auxiliary system adapted to connecting different branches of one well in yet another embodiment of the present invention, which implements both data transmission and casing detection. The difference between the present embodiment and the embodiment of FIG. 11 is that: a casing detection receiver 11 is mounted on the drill pipe segment above the insulating device of the currently drilling branch. Other structures of the present embodiment are the same with those of the embodiment of FIG. 11, and will not be described repeatedly herein.

FIG. 14 a˜f show schematic views of insulating device 17 mounted on the drill pipe in a preferred embodiment of the present invention. FIG. 14a shows a longitudinal sectional view of drill pipe 5 on which a surrounding insulating device 17 is mounted. FIG. 14b shows a transverse sectional view with respect to the A-A′ section in FIG. 14a of drill pipe 5. FIG. 14c shows a transverse sectional view basing on the B-B′ section in FIG. 14a of drill pipe 5. FIG. 14d shows a transverse sectional view with respect to the C-C′ section in FIG. 14a of drill pipe 5. FIG. 14e shows a transverse sectional view with respect to the D-D′ section in FIG. 14a of drill pipe 5. FIG. 14f shows a transverse sectional view with respect to the E-E′ section in FIG. 14 a of drill pipe 5. As shown in FIGS. 14 a˜f, in the present embodiment, drill pipe 5 is a hollow tubular drill pipe, and insulating device 17 includes an outer insulating device 18 mounted outside the drill pipe and an inner insulating device 19 mounted inside the drill pipe. It should be noted that, in other embodiments, the outer insulating device 18 and the inner insulating device 19 may also be separately used. When using separately, the outer insulating device 18 or the inner insulating device 19 can still suppress the current flowing into near formation or the mud inside the drill pipe, therefore the efficiency of data transmission and/or casing detection may also be improved in a certain extent.

In the foregoing embodiments shown in FIGS. 3˜13, for convenience of drawing, only insulating devices outside the drill pipes are shown. However, in fact, there may also be corresponding inner insulating devices inside the drill pipes. This will be readily understood to a person skilled in the art.

In additional, the insulating device may completely surround the enwrapped drill pipe segment with 360 degrees, or may partially surround the enwrapped drill pipe segment with less than 360 degrees. There may have one or more gaps in the insulating device, allowing the current to pass. The gaps on the insulating device may be in any shapes and at any positions in the insulating device, which may be used for controlling the direction of electric current (flowing in or flowing out) and the position of current flowing in or out. This will be easily understood to a person skilled in the art.

Said insulating device still may be an insulating sheet with a particular shape, thereby blocking the current at a particular position and/or azimuth. The shape of said insulating device may be square, ellipse or other regular shape, or irregular shape. This will be readily understood to a person skilled in the art.

Finally, it should be noted that the above embodiments are merely to describe the technical solutions of the invention, rather than limiting the scope of this invention. This invention can be extended to other modifications, variations, uses and embodiments in practice, without beyond the scope of the spirit and teachings of the invention. 

1.-16. (canceled)
 17. A drilling auxiliary system used for down hole EM data transmission and/or casing detection, wherein said drilling auxiliary system comprises an insulating device which is mounted on a drill pipe of a well and used for preventing entire current loss or suppressing partial current loss.
 18. A drilling auxiliary system according to claim 17, wherein said insulating device blocks or suppresses current flowing between the drill pipe and the medium surrounding the drill pipe, or blocks or suppresses current flowing between the drill pipe and the medium inside the drill pipe.
 19. A drilling auxiliary system according to claim 18, wherein said medium surrounding the drill pipe comprises formation adjacent to the drill pipe, said medium inside the drill pipe comprises mud inside the drill pipe.
 20. A drilling auxiliary system according to claim 19, wherein said insulating device surrounding said drill pipe is embedded into the wall of the drill pipe, or mounted on a position clinging to the drill pipe, or mounted on a position separated from the drill pipe.
 21. A drilling auxiliary system according to claim 19, wherein said drill pipe is tubular, and said insulating device comprises an outer insulating device and an inner insulating device, wherein said inner insulating device surrounds the inner wall of said drill pipe, and is embedded into the inner wall of said drill pipe, or mounted on a position clinging to or separated from the inner wall of said drill pipe; and wherein said outer insulating device surrounds the outer wall of said drill pipe, and is embedded into the outer wall of said drill pipe, or mounted on a position clinging to or separated from the outer wall of said drill pipe.
 22. A drilling auxiliary system according to claim 19, wherein said insulating device partially or completely covers the transmitting and receiving instruments mounted on the drill pipe.
 23. A drilling auxiliary system according to claim 19, wherein said insulating device completely surrounds the enwrapped drill pipe segment with 360 degrees, or partially surrounds the enwrapped drill pipe segment with less than 360 degrees.
 24. A drilling auxiliary system according to claim 19, wherein said insulating device is an insulating sheet with particular shape, for blocking the current in a particular position and/or azimuth.
 25. A drilling auxiliary system according to claim 24, wherein the shape of said insulating sheet is square, ellipse or any other shape.
 26. A drilling auxiliary system according to claim 23, wherein there are one or more gaps on said insulating device, and said one or more gaps allow the electric current to pass.
 27. A drilling auxiliary system according to claim 24, wherein there are one or more gaps on said insulating device, and said one or more gaps allow the electric current to pass.
 28. A drilling auxiliary system according to claim 26, wherein said gaps on said insulating device may be any shape.
 29. A drilling auxiliary system according to claim 26, wherein said gaps on said insulating device may locate at any position on said insulating device.
 30. A drilling auxiliary system according to claim 26, wherein said gaps on said insulating device is used for controlling the direction and/or the position of electric current flowing in or out.
 31. A drilling auxiliary system according to claim 23, wherein said insulating device enwraps or partially enwraps the insulating ring on the drill pipe and the partial or whole drill pipe segments which extend from the insulating ring in both directions.
 32. A drilling auxiliary system according to claim 23, wherein said insulating device enwraps or partially enwraps the insulating ring and the partial or whole drill pipe segment which extends from the insulating ring in one direction.
 33. A drilling auxiliary system according to claim 23, wherein said insulating device enwraps the partial or whole drill pipe segment which extends from the insulating ring in one direction. 